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January 28, 2007

Will alligators get you?

Will alligators get you? Do they present a danger to divers? And why am I thinking about it? Well, in part because I had that experience at Catfish Sink at Manatee Springs State Park where we went in despite having spotted that alligator. The sink was relatively large and the gator wasn't close, but there were a few tense moments of decision making nonetheless. We did go in and down to the bottom of the sink at 65 feet, but the instructor kept an eye on the gator who never left the surface and didn't bother us when we ascended. The subject of the gator has come up a few times since, and we've been joking how the gator grows larger every time we tell the story or think back of it.

Well, I was reminded of that while reading the late Sheck Exley's book "Caverns Measureless to Man." In it Exley describes an excursion into a sink with an alligator. The sink's surface was considerably smaller than Catfish Sink, perhaps 80 feet diameter, and Exley describes the 8-foot alligator as staring at them arrogantly, as if conveying that he was the master of this place. He went on describing whether or not the five of them, one without any kind of wetsuit protection, should go in or not.

They decided they would, primarily based on Exley's unequivocal statement that crocodilians could not withstand pressures deeper than ten feet, and so they'd be safe from the gator below that. All went well during the dive, but Exley describes how they performed their usual ten-feet decompression stop at 15 feet instead, beyond the assumed reach of the alligator. After that they made a quick exit out of the sink. Exley added that in that year, back sometime in the 1970s, there had been seven reported alligator attacks on humans, several of them fatal. He also reported that the great majority of the attacks had been done by alligators who had been fed by humans, and thus lost their fear of them. As it turned out, the gator in that sink had, in fact, been fed by humans. Two older ladies regularly stopped by to feed "Ollie" marshmallows.

That made me think. I had previously been trying to find references on the web as to how deep alligators dive, but had found nothing. I view Exley as an expert in all things diving, and especially diving in Florida where there are a lot of gators, and so his authoritatively stated position carries weight. Still, as I plan on diving in Florida again I hoped to get some more information.

Eventually I came across a website named crocodilian.com, an Australian site run by one Dr. Adam Britton who appears to be one of the world's foremost experts on crocodilian behavior. The site provided a ton of valuable information, but, again, nothing on depth. Dr. Britton invited questions, and so I sent him this email:


The late cave diving explorer and pioneer Sheck Exley stated in his book
"Caverns Measureless to Man" that crocodilians cannot handle pressure
below ten feet. So they decompressed deeper when alligators were

How deep do crocodilians dive?


I was pleasantly surprised to receive an email response from Dr. Britton within a day or so:

Hi Conrad,

There are reports from Lake Chamo in Ethiopia of crocodiles found below 60
feet, and I've had crocs on harpoon lines that sink to the bottom of tidal
rivers which are in excess of 10 feet deep, so Sheck Exley's statement
doesn't quite ring true. As to their maximum depth I really don't know, and
I am sure nobody else does either - virtually no work has been done in that
area, so we're relying on anecdotal observations. There are depth
monitoring devices that can be attached to transmitters, and when I get a
chance to use one I'll let you know!

Best wishes,


So there. In the light of this information, I wonder where Sheck got his information from. Obviously I can't ask him, and so we must assume that alligators can, and may, indeed dive deeper. This would be good information for divers to know. Attaching a depth monitoring device onto a crocodile or an alligator seems doable and I'd love to know the results of the data collected. As is, I'll probably judge any future alligator situations on a case-by-case basis. How many? How big? How close? Carol has been diving with gators present and says they always retreat when they see divers and I have no reason to doubt that. But knowledge backed by research is always a good thing. Oh, and for a fascination description of exploration of the Manatee Springs Cave System, click here.

Posted by conradb212 at 11:06 PM | Comments (0)

January 19, 2007

Caves and caverns

The first certification all of us earn is that of an "open water" diver. Open water? As opposed to what? Closed water? No, the "open" refers to the fact that you can go up and stick your head out of the water anytime. That's open water. Anything that's not "open water" is considered an "overhead environment." Examples of overhead environments are caves, caverns, going inside a wreck or diving under ice. When you dive in overhead environments you can't just go up if you're short on air. You first must find an exit. The implications of that are significant. And that is why diving in overhead environments requires additional training and certification.

This inevitably brings up questions. Diving in and by itself is wonderful. Breathing underwater, seeing all those sights, floating weightlessly. And the oceans are endless; it's not like you run out of things to see and experience. Why would anyone want to add to the risk by entering overhead environments that make everything more complicated and more dangerous?

Maybe it's just because the challenge is there, and people forever push the limits. Of all the dive books I've read so far, the majority deal with wreck diving and cave diving. The rest are generally introductions to scuba or textbooks on certain technical aspects, like specialized gear or diving physics. Caves and wrecks seems to be what fascinates a lot of divers, and some of the world's most famous dive sites are either wrecks or caves. Why?

I will always remember the night of my first dive in the pool, the first time I breathed underwater and we then went to the deep end of the pool. Apart from the sheer magnitude and thrill of the moment, the realization that I had done it and was breathing underwater, the one thing I remember most was how disoriented I felt. The world was essentially reduced to looking down or straight ahead and I never really knew where I was, even in the pool. At the time I attributed that to the newness of it all, and perhaps also to my black-skirted mask that did not allow glancing down or to the side. There's much discussion going on over what sort of mask is best, one that concentrates vision ahead or one that lets in as much light and vision as possible, but that's another topic. Fact is that orientation underwater, knowing where one is at all times, isn't easy, or at least it didn't come easy to me.

Even later, diving at Devil's Den in Florida, I didn't really know where I was most of the time. I know that because Carol asked me and I didn't know. And Devil's Den is a fairly confined environment. You swim around the big debris cone in the center and you can see the surface at all time. Devil's Den, of course, was new to me and when I dove there I still only had had a dozen dives or so to my name. But it also gave me my first glimpse of what an overhead environment might be like. Devil's Den isn't technically "overhead." Imagine a somewhat irregular sphere roughly halfway filled with water. There will be some places where the walls overhang. You look up and there is rock and you have to dive sideways and then up to the surface. That is still technically not even a cavern.

So what's a cavern and what's a cave? Definitions vary, but by and large a cavern is an underground area where you can still see the daylight within a certain distance and thus the exit. A cave is an overhead environment where you can't see daylight, or where daylight, and thus an exit, is so and so far away. The idea is that in caverns, you can always look around and see the exit. In caves you cannot see the exit and you must therefore know where you're going and what way is out. That is a huge difference. [The picture to the left is from the Tulum Cenote Dive Center in Mexico at cenotedive.com]

As a result, caverns and caves are treated very differently. Open water certified divers may dive in caverns, but only if accompanied by a cave-certified diver. Rules vary between agencies and locations, but all insist that anyone not trained in overhead environments have certified guidance. For cave diving, nothing other than true cave diving certification will do. There are also cavern diving courses and certifications, and they should be seen as sort of beginners classes towards "real" cave diving.

What makes cave diving so different? Different enough that rangers in certain dive sites that are mostly open water but do have caves (like the "Catfish sink" at Manatee Springs National Park in Florida) insist that you don't even take a dive light with you so as not to be tempted to go into the cave?

Well, I've never been in an underwater cave, but I've been in a few above ground. They are dark, and so you need a light. They can be narrow and constricting, and so you need to be comfortable in confined spaces. They are disorienting and you need to know the way out. And they tend to have offshoots that can easily turn them into maze-like labyrinths. Most people are somewhat intimidated by caves and some tend to panic. Now imagine being in a cave underwater where you have your dive gear on; where there are no lights on the ceiling of the cave and you need to bring your own; where there are currents and the possibility of poor visibility; and where you can run out of air. And where the cave may go deeper and you can't simply choose not to go that deep because that may be the only way through, or out. Wow.

As a result, cavern and cave training is very serious business. And the equipment used for cave diving is significantly more elaborate as well. Since you do need to see, you must bring a light along. But a light can fail. So you bring two, or better yet, three. Without air you're dead, and cave dives can be long and deep, so you bring along more air. Cave divers often use "doubles," dual tanks and a backup "pony" bottle to boot, and sometimes more. Since it is very easy to lose orientation, cave divers rely on lines. In well explored caves open as dive sites, there are permanent lines so that divers always know where to go, and which direction is out. But if a cave diver explores a new cave, running a new line and making sure it is tied off properly is a matter of life and death. And then there is the ever important visibility. Most caves have silt at the bottom, and fins can quickly stir that up to reduce visibility to almost zero. So if you lose your line and find yourself in a confined environment with zero visibility... you get the picture. What that means is that learning to fin without stirring up silt becomes a required skill.

If all this makes it sound like cave diving is dangerous, it is. A lot of people have died in caves, and not just new divers with inadequate training. So many divers died in Florida's caverns when they first became popular with sports divers in the 1970s or so that a lot of the caves were closed off and there was a real danger that all may be declared off-limits. The cave diving community realized that and, wisely, began developing procedures, training courses and materials, and required certification. Thanks to them, many of Florida's caves remain open, underground worlds that can apparently invoke thrills and bursts of adrenaline that I can only imagine at this point. Yet, even so, some caves are considered so dangerous that they were voluntarily blocked off. Even in Devil's Den I saw at least one grate that closed off an offshoot or cave entrance. Another is at the very popular Ginnie Springs.

Does that mean cave diving becomes completely safe once you have the proper training, certifications and equipment? The answer is no. It's dangerous. According to what I have read, the danger is highest to relatively inexperienced divers who go in and quickly panic. And to those who truly push the limits by exploring where no one has been before. One such maverick was Sheck Exley, the man who literally wrote the book on cave diving (several, actually). In 30 years he logged 4,000 cave dives. He was a meticulous, safety-conscious planner and perfectionist who continually and systematically advanced the state-of-the-art in a methodical -- not reckless -- manner. Yet, in the end his quest to go ever deeper cost him his life. In April of 1994, after having reached cave depths of a mind-boggling 881 feet on Trimix and other gasses, Exley went for a round number -- one thousand feet -- at Zacaton cave (a sinkhole, or "cenote," really) in Mexico. He did not come out alive (for details, click here).

What drives mankind to attempt such exploits? Is it a death wish, seeking thrills, an adrenaline rush, or pushing the state-of-the-art? What separates doable progress from reckless impossibilities? No one would, for example, shoot for being the first person to do a space walk without a suit. You can't. Diving a thousand feet deep into a cave seems almost as physically impossibly, yet somehow Exley concluded it was still within the limits of human endurance and possibility. It wasn't.

Maybe each of us has our own comfort level. Will I ever dive caves? I have no idea. Will I dive caverns? Most likely. The pictures I've seen look beautiful. Why do I even contemplate all this when I am still a total newcomer to the sport of scuba diving? Maybe for the same reason that drove me to write a detailed FAQ on superchargers for import cars before I had ever installed, tuned or even driven a supercharged vehicle -- and then have the audacity to publish it on an enthusiast website. I was ridiculed at first, but ended up its moderator and resident expert for a while. I love to learn about the more complex and extreme issues of everything I become involved in. I am a meticulate researcher and can quickly grasp concepts and sort of become an expert in any given field. I eventually did participate in the development of a supercharger for my vehicle, learned how to electronically tune it via a sophisticated computer-based engine tuning system, and then datalog everything at the racetrack. Learning theory first, then practice works for me.

I think back of being at the bottom of Catfish Sink at Manatee Springs State Park, near the entrance to the cave that connects the sink with the next open water basin about 500 feet downstream. Even just outside the siphon of the cave entry the walls were black. Carol and Ted had gone through there early on in their diving careers, just a year or two into it, duly certified for cave diving, of course. I asked her how it was inside, what one feels. She didn't tell me much. Maybe it's something one has to experience.

Posted by conradb212 at 11:05 PM | Comments (0)

January 17, 2007

Thoughts about rebreathers

A year or so before I got into scuba I saw a remarkable, though rather corny, movie that contributed to my desire to see the world underwater, and also led to another interest. The film was "The Cave," a weird combination of gorgeous diving and underwater cave photography and a B-movie horror plot of evil creatures decimating a team of divers in spite of their modern technology. One such piece of technology was a "rebreather" that enabled them to be underwater much longer. For all I knew back then, that rebreather was just fiction. Now, of course, I know that it is not. It's a scuba unit that tackles the challenge of breathing underwater in a different, and arguably more elegant, way.

Simply put, a rebreather recycles the air we breathe, taking advantage of the fact that humans only use a small fraction of the oxygen that is in every breath we take. It scrubs out the carbon dioxide and uses various mechanisms to keep things in balance. The result is a smaller scuba unit that nonetheless allows much longer bottomtime, and also makes for a far less intrusive diver because, depending on the type of rebreather, there are no bubbles, or far fewer. (The picture on the left shows a Draeger rebreather unit I saw during a dive at Lake Tahoe. Note the very small Nitrox tank.) It's easy to see how such a device can fascinate. I hate waste in any shape or form, and the rebreather wastes nothing. I am also not fond of needless work, and shlepping around far more gear than a more elegant technology allows seems nonsensical. With all those advantages, why aren't rebreathers everywhere?

That is a good question. They've actually been around far longer than conventional scuba units. Long before Cousteau and friends tested the first demand valves and the "Aqua Lung," divers had been using rebreathers. In fact, they've been used for almost 130 years. And not just in theory but in actual commercial work, going back to the end of the 19th century (in 1880, a rebreather design by Englishman Henry Fluess was successfully used to close a sluice door in a flooded tunnel). Of all the diving books I've read that touch upon rebreathers in any way, half seem to view them as some sort of specialized technology that will never be viable for sports diving. The other half see them as the future of scuba.

So why aren't we all using rebreathers? The simple answer is safety. It's not that rebreathers aren't safe if used properly, it's just that they are infinitely more complex than conventional scuba, and when it comes to the air we breathe underwater, there is no margin for error.

See, scuba, despite all the remarkable technology that goes into all those sophisticated first and second stages, is really a simple concept. Compress a lot of air into a tank, then breathe it. Sure, there are dive physics which affect how we breathe air underwater and there are physiological aspects to consider -- like the impact of nitrogen on our bodies -- but for that we have dive computers and training. But by and large, scuba is a simple process: use compressed air. It is a passive technology.

Rebreathers, on the other hand, are complex as there are many more factors to consider. Yes, you use the air you bring underwater with you much more efficiently, but that comes at a price. If the chemicals used to "scrub" the carbon dioxide out of the air fail, you can die without even noticing that anything is wrong. If something in the oxygen delivery system malfunctions you may either get too much or too little oxygen and, again, you can die. If the whole complex rebreather mechanism isn't maintained meticulously, it may fail or become contaminated, again with ominous consequences. So there. Rebreathers are an elegant technology but just about the opposite of the famous "fail-safe" ("fail-safe" meaning that when a component fails it defaults to safe). If a scuba regulator fails and starts free-flowing, you're "safe" because you continue to get air (albeit not for long); if a rebreather fails, it fails in a bad way.

So that's all bad news, but not enough to write the technology off. We humans routinely deal with dangerous technology that is safe because we made it so. If an airplane fails, the consequences are usually deadly, but we accept that risk because the technology has advanced to a point where the risk is very small. Heck, even home heating systems are essentially deadly, but we all have one. The difference is that millions use air travel and billions a heater, whereas only very few use a rebreather, hence the development of the technology is far slower.

Another issue with rebreathers is that there are different rebreather technologies. With some there are no bubbles at all. That's because with them you breathe pure oxygen and so there is no waste. The body uses part of the oxygen gas, the rest is cleansed and used again. Problem is that those can only be used in very shallow depths. Go deeper and the higher partial oxygen pressure makes oxygen toxic to our bodies and the result is a seizure. So this technology is primarily used for military purposes where the total absence of telltale bubbles is mandatory.

Most rebreathers are semi-closed, which means you do use some other gas, nitrogen. That way you can go deeper, which means pressure differences and therefore the need to be able to expell some gas. The advantage here is that oxygen and nitrogen can be combined any which way, or come from different tanks, which means the breathing gas can be mixed to the best advantage at any given depth. With less nitrogen to worry about, yet rebreathing technology that makes maximum use of oxygen, bottom times can be much longer. More complex units may add helium to the equation so that you can go deeper yet without experiencing nitrogen narcosis.

The problem is clear: how to add oxygen properly, sufficiently and reliably at all times, and how to measure its presence. So we're dealing with an inherently more complex technology that can turn deadly in an instant, one that requires extensive understanding and training and meticulous maintenance, and one that costs a whole lot more. That is the reason why rebreathers are the exception and not the norm, for now. I've only begun to learn about rebreather technology. There will undoubtedly be more entries on this topic. And I may end up using one at some point.

Posted by conradb212 at 11:05 PM | Comments (0)

January 08, 2007

Of cards

There was a time in my life where credit cards were very important to me. Maybe that's because I didn't grow up with them. We paid in cash, everything. When I moved to the United States to attend post-graduate courses at Rensselaer Polytechnic Institute in upstate New York, credit cards still weren't important. I think the first time I realized their value was when a friend from Europe visited and I had to put up a huge cash security deposit for a car rental because I did not have a credit card. So I got into the game. Department store cards came first. They had ridiculously low credit limits, and I quickly learned that paying on time was a must. One time I had a card refused at Montgomery Ward because an $8.81 balance was late.

Getting my first "real" credit cards was a revelation and soon I went on a literal collection spree, applying for everything. When I got my first real job after graduating from RPI I had an American Express card and then soon a Diner's Club card and a Carte Blanche. Yes, those two still meant something in those days. At some point I got an American Express Gold card which I was hugely proud of, especially when I visited friends in Europe where it was much more difficult to get a "gold card."

That era of credit card obsession is now ancient history. Today I view them as a pain more than anythging, as a minefield, a necessary evil. I routinely ditch the junkmail that offers yet another card, and I instinctively distrust any offer even from my own banks. I fully expect to get ripped off with obscene "late fees" or other dubious charges, and I fully expect the banks to fudge a bit so as to make me "late" so they can jack up my interest rate and report me to the credit bureaus. Yes, it's come to that. These days I almost exclusively use debit cards, drawing from money that is already mine and in my bank account. Cards are a pain, and we have far too many of them weighing down our valets.

However, there are exceptions. There are two cards that I would truly never leave home without, and those are my diver certification cards. Yes, I know it's silly, but I am more proud of my PADI Open Water Diver card and my NAUI Advanced Scuba Diver card than I ever was of any prestigious credit card. Maybe it is because I truly earned those cards, because I had to study for them, then dive underwater where humans are not supposed to be able to breathe. Maybe it's because they are tangible evidence that I succeeded at something that has become a passion of mine, diving. Maybe it's because of the signatures on those cards, the signatures of the people who opened this wondrous new world to me, enriching my life in so many ways.

I know, of course, that collecting certification cards has nothing to do with real diving experience. Despite my cards I am still of newbie scuba diver with little underwater experience, experience that I will only accumulate with the many more dives I plan on making in the years ahead. But I already know that I'll cherish each and every new C-card.

Posted by conradb212 at 11:04 PM | Comments (0)

January 03, 2007

Scuba and fitness

Recently I've thought a lot about how fit you need to be to be a scuba diver. Opinions on this vary greatly. Everyone knows and agrees that being a good tennis player or golfer takes a lot of practice. And few would dispute that athletes and ball players must work out and keep themselves in top physical condition. Things get a bit murkier with sports like auto racing. Does a NASCAR driver have to be physically fit? Some say not, but I tend to believe one must be in top physical shape to withstand the heat and g-forces and manhandling of the pedals and steering wheel over hours of racing.

But scuba? I mean, we constantly point out how wonderful it is to effortlessly float in the water, how our goal should be to expend as little energy as possible, and how nice and relaxing it is down there. During my PADI open water classes I was surprised to learn that, apparently, the average scuba diver is a male in his early 50s who is overweight and smokes. Not exactly the image of a physically fit specimen, and certainly not the image of the young, sleek, suntanned surfer-type scuba divers of both genders we see in ads and commercials.

So do scuba divers need to be fit? In their manuals and course materials, training agencies repeatedly point at fitness as a key requisite for scuba diving. We're not talking specific workouts or training programs, just general good health and a state of fitness. Smoking is a strong negative for divers not only because it affects fitness, but also because carbon monoxide from smoking has a much greater affinity to hemoglobin in our blood than oxygen. Hemoglobin carries oxygen, and that means the extra carbon monoxide in smokers' bodies reduces the amount of oxygen the blood can carry. So smoking before diving is a very bad idea.

But fitness in general? I've read books and articles claiming that scuba diving is among the least physically demanding sports of them all. Just plop in the water and float. I've seen tables that show calories burned while diving and it is supposedly nowhere near as much as for some of the rigorous physical sports out there. Even size and weight isn't that much of an issue. Sure, fat has a greater tendency to absorb nitrogen and the larger amount of nitrogen absorbed can thus play a role in decompression. However, there are a good number of fat divers who are total experts and they manage just fine.

My personal experience so far has been that fitness does matter when it comes to scuba diving, but it matters in a different way. It is absolutely true that gracefully floating underwater requires very little physical exertion. But the same is most definitely not true when it comes to carrying around equipment or gearing up. I am physically quite fit, yet hefting around scuba tanks can be demanding. Even getting up and walking the short stretch from a base camp to the water can be quite difficult. Whenever I see technical divers with dual tanks, I wonder how they ever manage out of the water. And cave divers with all their gear and even more tanks? Try that if you're not in good shape.

I cannot help but feel that the short bursts of energy required to move around in scuba gear have the potential of overwhelming an unfit, or even marginally fit, person. And given that a good percentage of the adult population suffers from chronic lower back pain, I wonder how many of those "typical" middle-aged divers incur back injuries from the equipment.

And then there are exertions one would not even think of, like donning a wetsuit. In my experience, putting on a tight-fitting 7mm wetsuit in warm weather can be equivalent to a major workout. When I put on mine, admittedly a nice and tight fit, I usually sweat bullets and breathe heavily by the time I'm all done and suited up. And unless I rest for a few minutes to catch my breath and cool down before I go under, I suck up half a tank just recovering from gearing up. When I did my NAUI advanced diver checkout dives this past Fall, I marveled at how easily Carol managed to carry and don her gear. It's because as an experienced scuba instructor she is in top shape and used to carrying all that heavy equipment. Fitness does matter.

It also matters in another way. The air in a scuba tank disappears frightfully fast. Due to the laws of physics it gets consumed faster the deeper you go, and there is nothing we can do about that. What we can do is control the rate of air consumption. Heavy breathers can empty a tank in a fraction of the time the same air lasts an experienced diver. That's in part because experienced divers will not needlessly exert themselves, but also because they have learned to control their breathing. And that, again, requires fitness. A fit person is able to return their breathing to normal much faster than an unfit one.

So as far as I am concerned, fitness matters in scuba.

Posted by conradb212 at 11:04 PM | Comments (0)